Conrad Johnson LP 125 SA stereo
The latest in the highly regarded series of conrad-johnson vacuum-tube power amplifiers, the LP125sa represents a compelling combination of the audio excellence one expects from conrad-johnson, the convenience of a single stereo chassis, and, at 125 watts per channel, sufficient power for the majority of high-end speaker systems. This is an amplifier capable of capturing the delicate textures and subtle nuances of live music while maintaining control with the authority that comes with ample power.
The LP125sa audio circuit consists of three stages. The input signal is amplified by a single-ended triode amplifier designed for wide bandwidth. The signal is then direct coupled to a cathode coupled phase-inverter. This high current, triode phase-inverter stage provides a balanced, low impedance drive to the output stage. Output power is developed by two pairs of KT120s per channel, chosen for their excellent sonic character, high power, and reliability. The output tubes are operated in ultralinear configuration which offers a desirable combination of high power and low distortion. Massive output transformers with intricately interleaved windings afford extended bandpass and high phase linearity. A small amount (about 12 dB) of loop negative feedback reduces distortion and achieves a sufficiently high damping factor to control reactive loudspeaker systems.
Power supply design is every bit as critical to the performance of an audio component as the audio circuit itself. In the LP125sa, separate, low impedance, discrete dc power supply regulators are provided for the input and phase-inverter stages, preventing the output stage from modulating these stages through the power supply.
These amplifiers require no complicated adjustments or specialized equipment to maintain. To assure continued peak performance, the owner need only make a simple bias adjustment when new tubes are installed. Built in LED bias indicators allow the user to make this adjustment using only the supplied screwdriver.
At conrad-johnson we are keenly aware that component parts contribute importantly to the sonic performance of any circuit design. As expected for conrad-johnson products, the LP125sa amplifier sets uncommonly high quality standards. Resistors are precision metal film types. All audio-circuit capacitors, as well as all capacitors in the regulated power supplies are polypropylene and polystyrene. Proprietary wide-bandwidth output transformers contribute to excellent high frequency performance. Even the gold plated connectors and the internal wiring have been carefully selected for optimal sonic performance. The LP125sa offers fine tube performance that ìjust sounds rightî. Those who wish to take the experience a step further will want to investigate the upgraded LP125sa+ which incorporates CJD Teflon Capacitors and ultra high-performance metal foil resistors in strategic applications in the circuit. Either model is sure to rekindle your passion for enjoying great music in your home.
Power: 125 watts per channel from 30 Hz to 15 KHz at no more than 1.5 % THD or IMD, both channels driven into 4 ohms (also available connected for 8 or 16 ohm loads)
Sensitivity: 1.1 volt rms to rated power
Frequency Response (at 10 watts):20 Hz to 20 kHz, +/- .1 dB
Hum and Noise: 104 dB below rated power
Input Impedance: 100 kOhms
Tube Complement: 1x 6189, 2x 6N30P, 8x KT120
Dimensions: 19D x 19W x 8H
Weight: 41 kg